This invention relates to an improvement in the process of preparing wrinkle resistant textile fabrics.
Specifically, this invention relates to an improvement in the process of preparing wrinkle resistant fabrics containing cellulosic fibers by impregnating said fabric with an N-methylol type durable press resin and curing said resin-treated fabric.
This invention further relates to an improvement in the process of preparing wrinkle resistant fabrics containing cellulosic fibers by impregnating said fabric with an N-methylol type durable press resin and curing said resin in the presence of sulfur dioxide.
Wrinkle resistance and durable press properties in textile fabrics are well established and are of great importance and economic value to the textile industry. The majority of textile articles, both wearing apparel and household articles, available in the marketplace exhibit these properties to some beneficial degree. Although many synthetic fibers inherently possess resiliency and wrinkle resistance, fabrics containing cellulose fibers must be chemically treated to acquire these important properties needed for the modern textile market.
The principal chemical treatments which produce wrinkle resistance and durable press properties in cellulose containing textiles are those in which the cellulose molecules are crosslinked, generally by reaction of a di- or polyfunctional agent with the cellulose. Many of the agents employed by the textile processing industry to produce durable press properties in cellulosic fabrics are N-methylol adducts. To enhance the reactions between the cellulose and these adducts many compounds or catalysts may be employed.
The process is known to use sulfur dioxide as a catalyst with formaldehyde to cross-link cotton fabrics and thereby impart and improve the wrinkle recovery angles of the cloth. Wilson and coworkers, Textile Research Journal, Volume 38, 1968, page 401, have used gaseous techniques employing sulfur dioxide and formaldehyde in finishing cellulose-containing textiles. The strong protonic acid, hydroxymethanesulfonic acid (HMS), resulting from the reaction of sulfur dioxide, formaldehyde and water in the treatment is "self limiting" in that it dissociates as the fabric dries so that the components volatilize to give a built-in safety mechanism against over reaction or acid degradation. The HMS is formed in situ on the cloth to catalyze the curing of a durable press resin. Moisture content of the textile with sulfur dioxide and formaldehyde curing is critical. If the moisture content is above 14%, much of the reaction occurs under swollen conditions. Under such swollen conditions the fiber cannot collapse to the extent necessary to develop useful dry wrinkle resistance. There is difficulty in adjusting the moisture content to about 14% at a temperature below that at which much crosslinking takes place. Due to the undesirable properties of formaldehyde, there is a growing trend in the fabric finishing industry to reduce the use of formaldehyde.
Reinhardt, Kullman, Cashen and Reid determined that HMS is effective as a catalyst for durable press finishing of cotton and polyester/cotton fabrics. MHS is a strong acid and can be used in relatively small concentrations. Reinhardt et al developed an odor-free process for preparing HMS for use as a catalyst which is the subject of U.S. Pat. No. 3,878,123. HMS can be prepared in situ in the pad bath during which the fabric is impregnated with the durable press resin. The acid is readily formed upon the addition of sulfurous acid to pad baths containing free formaldehyde or it can be prepared separately. Sulfurous acid is readily formed by dissolving sulfur dioxide in water. The HMS dissociates when the fabric becomes dry during finishing to yield components which are readily volatilized from the fabric. An after wash is not necessary to prevent loss of strength or wrinkle resistance subsequent to curing.
Reinhardt and Kullman have further studied sulfonic acids and sulfonate salts as catalysts in durable press finishing. Textile Research Journal, Volume 47, 1977, page 181. Included in the study were alkyl, substituted alkyl and aromatic sulfonic acids and ammonium, amine and metal sulfonate salts. The sulfonic acids were shown by Reinhardt and Kullman to be strong catalysts for durable press properties at low concentrations. The sulfonate salts were shown, generally, to be more moderate catalysts than the acids.